1. Field of the Invention
The present invention relates to non-contact means for moving insulative material to a selected location, in general, and to an electrostatic charge-controlled material positioning system for precisely positioning such material to an assembly machine workstation, in particular.
2. Description of the Prior Art
Various types of intermittent motion machines are presently available for registration purposes or for positioning portions of a web or individual pieces of material to a selected location or assembly machine workstation with varying degrees of precision. The means for determining when material has been properly positioned to a particular location in these types of machines may be conveniently thought of as falling into either one of two general categories. In one category, physical contact is made between the material to be positioned and the sensing means that determines when the material is positioned to a selected location. In the other category, a material-position determining sensor would sense material position without making physical contact with the material.
In intermittent motion machines incorporating the contact-type sensor mentioned above, the shape of material to be positioned normally is permanently altered in order for it to properly cooperate with the position determining sensor that senses when the material has been positioned to a selected location. Such alterations increase costs in that means must be provided to produce such alterations, and very often more material is required either because of the altered portion of the material being unsuitable for other uses, or having to provide additional materials so that it can be altered for subsequent cooperation with a contact-type material position sensor.
Prior art intermittent motion machines of the non-contact type usually rely on substances being applied to the material to be positioned in order to indicate actual material position. In U.S. Pat. No. 3,977,586 to HERTRICH, for example, light reflecting surfaces are added to the material to be positioned. As suggested in the HERTRICH patent, magnetic material could also be added to the material to be positioned and a magnetic sensor would then be employed to determine when the material had been positioned to the desired location. The addition of such substances to the material to be positioned would also add to overall costs both for providing the substance to be added and for placing it on the material. In addition, that portion of the material on which the substances are deposited may not be available for use in the finished end product which would reduce material yields and thereby increase material costs.
A primary object of the resent invention is to provide apparatus for determining the position of a portion of an insulative material with respect to a selected reference frame or position.
Another object of the present invention is to provide material position determining apparatus that does not physically contact the material for material position-determining purposes.
A further object of the present invention is to provide material positioning apparatus that will not produce permanent physical alterations in the material to be positioned.
Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of a preferred embodiment thereof when taken in conjunction with the accompanying drawings.